1) Field
The disclosure relates to a multiple surface acoustic wave (“SAW”) sensor system, more particularly, to a multiple SAW sensor system capable of sensing a plurality of target materials in the SAW sensor with a single detector by using a multiplexer.
2) Description of the Related Art
A Surface Acoustic Wave (“SAW”) sensor is an element or a device for detecting or measuring an absolute value of a physical quantity or a chemical quantity, a change in physical quantity or chemical quantity, or intensity of a sound, light, or a radio wave from a target using a base and surface sensing technique and a SAW, and for converting them into an electrical signal.
Generally, the SAW sensor is disposed on a substrate made of a piezoelectric material, and includes a receptor that binds to a target material on a surface of the SAW sensor. Thus, when a sample containing the target material flows to the SAW sensor, a wavelength is changed due to a physical, chemical or electrical reaction between the target material and the receptor. The resulting change is used to determine or monitor the content of the target material.
For a biosensor, when a biomolecule, such as a protein, antibody, antigen, deoxyribonucleic acid (“DNA”), ribonucleic acid (“RNA”), bacteria, an animal cell, a virus or tissue, and a toxin generated therefrom, binds to a surface of the biosensor, a surface mass of the sensor changes, and thereby a signal drift occurs in the sensor. As a result, the biosensor can determine or monitor the content of the target material.
Methods for monitoring the change of a wavelength in the SAW sensor are generally divided into two types. A first type is an oscillation method of checking the change of the wavelength in the SAW sensor by re-applying an output signal emitted from the SAW sensor to the SAW sensor as an input signal. A second type of method for monitoring the change of the wavelength in the SAW sensor is measuring the change of the wavelength by applying a specific frequency, generated outside the SAW sensor, to an input inter-digital transducer (“IDT”) electrode of the SAW sensor and plotting output signals according to frequencies.